multithreading - 在等待线程完成时显示 progressDialog 2 秒

Question

我有一个 Activity ，我在其中调用了一个服务，该服务可能需要一段时间才能完成，直到该服务没有完成，单击的菜单选项应该返回一条错误消息，例如“数据尚未准备好，请重试很快”但是，我想在抛出该错误之前给它几秒钟的时间来完成，在此期间，我想在屏幕上显示一个进度对话框。这是我的代码:

if(calculatedValue.equals(NOT_YET_CALCULATED)){
                //show progress dialog
                ProgressDialog progress = ProgressDialog.show(this, "", getResources().getString(R.string.wait), true);
                long timeStarted = System.currentTimeMillis();
                while(calculatedValue.equals(NOT_YET_CALCULATED) && System.currentTimeMillis() - timeStarted < 1500){
                    // wait for at most 1.5 seconds
                }
                progress.dismiss();
                if(calculatedValue.equals(NOT_YET_CALCULATED)){
                    //if it's still not there, there's probably a problem, show generic alert dialog
                    AlertDialog dialog = new AlertDialog.Builder(this).create();
                    dialog.setTitle(R.string.not_yet_calulated_alert_title);
                    dialog.setMessage(getResources().getString(R.string.not_yet_calulated_alert_message));
                    dialog.show();
                }else{
                    startActivity(j);
                }
            }else{
                startActivity(j);
            }

让我解释一下:我检查该值是否存在，如果不存在，我会显示一个进度图标(我要画圆圈)1.5 秒。如果在那之后它仍然不存在，我会放弃并显示一条错误消息。

问题是屏幕上没有显示进度。我做错了什么？

谢谢，即.

Answer 1

明白了，应该为此使用异步任务，这是代码:

    if(calculatedValue.equals(NOT_YET_CALCULATED)){
    //show progress dialog
    final ProgressDialog progress = ProgressDialog.show(this, "", getResources().getString(R.string.wait), true);
    AsyncTask<Void, Void, Boolean> waitForCompletion = new AsyncTask<Void, Void, Boolean>(){
        @Override
        protected Boolean doInBackground(Void... params) {
            long timeStarted = System.currentTimeMillis();
            while(calculatedValue.equals(NOT_YET_CALCULATED) && System.currentTimeMillis() - timeStarted < 1500){
                // wait for 1.5 ms
                 try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        Log.e(TAG, "thread interrupted", e);
                    }
            }
            progress.dismiss();
            return calculatedValue.equals(NOT_YET_CALCULATED);
        };
        @Override
        protected void onPostExecute(Boolean result) {
        if(result == true){
            AlertDialog dialog = new AlertDialog.Builder(TodayActivity.this).create();
            dialog.setTitle(R.string.not_yet_calulated_alert_title);
            dialog.setMessage(getResources().getString(R.string.not_yet_calulated_alert_message));
            dialog.show();
        }else{
            i.putExtra(Constants.AMOUNT, Integer.parseInt(calculatedValue));
            startActivity(i);
        }
        }
    };
    waitForCompletion.execute(null, null, null);
}else{
i.putExtra(Constants.AMOUNT, Integer.parseInt(calculatedValue));
startActivity(i);
}